Decoupling of inorganic and organic carbon during slab mantle devolatilisation

Serpentinites are an important sink for both inorganic and organic carbon, and their behavior during subduction is thought to play a fundamental role in the global cycling of carbon. Here we show that fluid-derived veins are preserved within the Zermatt-Saas ultra-high pressure serpentinites providing key evidence for carbonate mobility during serpentinite devolatilisation. We show through the O, C, and Sr isotope analyses of vein minerals and the host serpentinites that about 90% of the meta-serpentinite inorganic carbon is remobilized during slab devolatilisation. In contrast, graphite-like carbonaceous compounds remain trapped within the host rock as inclusions within metamorphic olivine while the bulk elemental and isotope composition of organic carbon remains relatively unchanged during the subduction process. This shows a decoupling behavior of carbon during serpentinite dehydration in subduction zones. This process will therefore facilitate the transfer of inorganic carbon to the mantle wedge and the preferential slab sequestration of organic carbon en route to the deep mantle.

Development of a sample preparation procedure for Sr isotope analysis of Portland cements

The 87Sr/86Sr isotope ratio can, in principle, be used for provenancing of cement. However, while commercial cements consist of multiple components, no detailed investigation into their individual 87Sr/86Sr isotope ratios or their influence on the integral 87Sr/86Sr isotope ratio of the resulting cement was conducted previously. Therefore, the present study aimed at determining and comparing the conventional 87Sr/86Sr isotope ratios of a diverse set of Portland cements and their corresponding Portland clinkers, the major component of these cements. Two approaches to remove the additives from the cements, i.e. to measure the conventional 87Sr/86Sr isotopic fingerprint of the clinker only, were tested, namely, treatment with a potassium hydroxide/sucrose solution and sieving on a 11-µm sieve. Dissolution in concentrated hydrochloric acid/nitric acid and in diluted nitric acid was employed to determine the 87Sr/86Sr isotope ratios of the cements and the individual clinkers. The aim was to find the most appropriate sample preparation procedure for cement provenancing, and the selection was realised by comparing the 87Sr/86Sr isotope ratios of differently treated cements with those of the corresponding clinkers. None of the methods to separate the clinkers from the cements proved to be satisfactory. However, it was found that the 87Sr/86Sr isotope ratios of clinker and cement generally corresponded, meaning that the latter can be used as a proxy for the clinker 87Sr/86Sr isotope ratio. Finally, the concentrated hydrochloric acid/nitric acid dissolution method was found to be the most suitable sample preparation method for the cements; it is thus recommended for 87Sr/86Sr isotope analyses for cement provenancing. Graphical abstract

Determining 88Sr/86Sr of barite using the Na2CO3 exchange method

This study presents a method of high precision stable Sr isotope measurement for barite using the Na2CO3 exchange reaction and MC-ICP-MS. The reliability of this method was strictly tested by...

Measurements Isotopic Ratios Signature and Level Concentration of Pb and Sr from Several Romanian Wines

Authenticity, certification, and especially the origin of food has become an increasing priority among consumers and producers, in the case of wines, this is very important especially if commercial values are associated with the region of production. In the last decades, isotopic ratios of geological interest, such as Pb, and Sr, have gained interest in the tracking regional provenance of foods and especially of wine. The correlation of the Pb and Sr isotope ratios between soil and plant makes it an interesting tool for tracing the provenance of agricultural products such as grapes and wine. The purpose of this research was to assessment the Pb and Sr isotopic ratio to highlight geographical markers with a high degree of credibility in several Romanian wine-growing areas. The values of the 206Pb/207Pb, for the vine from Dealu Bujorului and Valea Călugărească vineyard show traces of lead atmospheric pollution, in Nicorești, Panciu, and Ștefăneți-Argeș vineyard the values of the isotopic ratio show traces of fly ashes, coals, or natural Pb and Greaca vineyard show traces of petrol, gasoline, combustion. Due to Pb, and Sr a separation on the vineyards and wine-growing centers, and also a separation of the wine samples was possible.